Banner Sizes
There are no official requirements for banner ads, other than the specifications given by individual advertisers. However, the following is a list of the most common ad sizes. Click the titles to view a banner example:

Full Banner - 468 by 60 pixels. The Full Banner is the most common size. An alternate size is 392 by 72 pixels for Full Banners with vertical navigation bar.

Half Banner - 234 x 60. Aptly named, if you put two Half Banners side-by-side, they equal a Full Banner.

Square Button - 125 by 125 pixels. Smaller banners are considered "buttons". The Square Button is commonly used in vertical navigation bars.

#2 Button - 120 by 60 pixels. This button works great with the other buttons in vertical layouts and used in conjunction with the Full and Half Banners in horizontal layouts. A Full Banner does not span a 640-pixel web page width so you can add a No. 2 Button to fill the space.

Vertical Banner - 120 by 240 pixels. A great alternative for either a vertical version of the banners, or a larger version of the buttons.

Micro Button - 88 by 31 pixels. It's all in the name: a great tool for brand advertising.